In a nitride single crystal growth process according to for instance an ammonothermal process (see Patent Document 1), in an ammonia atmosphere under a supercritical state (temperature: 405.6K and pressure: 11.3 MPa at a critical point of ammonia), a nitride single crystal such as gallium nitride or the like is grown. The supercritical ammonia that is high in the temperature and pressure is very large in the corrosiveness; accordingly, in a reactor such as a high temperature and pressure vessel or the like, a countermeasure for inhibiting the corrosion is very important. Furthermore, a mineralizer (chlorine-based compounds) added to the supercritical ammonia when a nitride single crystal is grown further increases the corrosiveness.
In the existing technology, in order to inhibit the corrosion, a method where an apparatus portion that comes into contact with a supercritical fluid is covered with a noble metal such as Pt, Ir or the like, or an alloy or oxide thereof is proposed (see Patent Documents 2 and 3).
Patent Document 1: JP-A-2003-277182
Patent Document 2: JP-A-2001-170478
Patent Document 3: JP-A-2002-361069